Water contamination in aircraft fuel tanks can cause many problems with the aircraft fuel systems. As the aircraft reaches altitude, the ambient temperature drops to around −50° C. which leads to ice formation in the fuel tank. This can lead to gauging errors and failures, clogging of the fuel pumps and interference with fuel pump pressure switches. The presence of water in the fuel tank can also lead to the growth of micro biological contamination (MBC) which can lead to similar problems. It is therefore desirable to remove the water from the fuel tank before these problems occur.
A conventional method for draining water from fuel tanks involves providing water drain valves on the floor of the fuel tank. However, these water drain valves are typically unable to discriminate between water and fuel. The consequences of this are that fuel is lost from the tank when water is drained and that often insufficient water is removed to prevent the above problems. Moreover, an operator is required to drain the water from the fuel tanks when the aircraft is grounded. This method is therefore also expensive and time consuming.
“Unimpeded Permeation of Water Through Helium-Leak—Tight Graphene-Based Membranes”, R. R Nair et al, Science, 27 Jan. 2012, Vol. 335, no. 6067, pp. 442-444, DOI:10.1126/science.1211694 (referred to below as “Nair et al”) demonstrated that that submicrometer-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors, and gases, including helium, but these membranes allow unimpeded permeation of water.